The conventional catalytic Claus process for sulfur recovery from sulfur containing gas streams is widely practiced and accounts for approximately one half of total sulfur production. However, the effluent tail gas from a final of a series of reactors in a Claus plant can contain varying quantities of different compounds including sulfur, water, hydrogen sulfide, sulfur dioxide, carbonyl sulfide, and carbon disulfide as well as other compounds.
Strict environmental standards on sulfur emissions require in many cases a further reduction in the total quantity of sulfur compounds present in a Claus plant tail gas. As a result, a number of Claus plant tail gas cleanup processes have been developed. Certain of these processes share a process sequence in which water, a reaction product of the Claus conversion, can be removed thus favoring further removal of sulfur compounds by Claus conversion.
One such process is described in Beavon, Canadian Pat. No. 918 384 (1973) which hydrogenates a Claus plant tail gas stream to convert all sulfur compounds to hydrogen sulfide followed by cooling the resulting hydrogen sulfide containing stream in a contact condenser to remove water, and optionally followed by a desiccator to further reduce water content, before further Claus conversion.
Another such process is described in "BSR/Selectox I Sulfur Recovery Process for Claus Tail Gas Treating," by Beavon and Hass, presented at the Fifth Canadian Symposium on Catalysis, Oct. 26-27, 1977, which discloses a process for removal of sulfur from a Claus plant tail gas stream by hydrogenating the Claus tail gas stream to convert all sulfur compounds to hydrogen sulfide followed by cooling the resulting stream in a contact condenser to remove water, introduction of a source of molecular oxygen, for example, air, and direct oxidation of hydrogen sulfide to sulfur over a proprietary Selectox-32 catalyst.
A process which can utilize contact condensers to remove water from an hydrogenated Claus plant tail gas stream followed by Claus conversion (reaction of hydrogen sulfide and sulfur dioxide to form elemental sulfur) in the absence of free oxygen is described in copending application Ser. No. 343,661, filed Jan. 28, 1982, which discloses hydrogenating a Claus plant tail gas stream to convert all sulfur compounds to hydrogen sulfide, cooling the resulting stream at least in part in a contact condenser (quench tower) to remove water, converting at least a portion of the resulting hydrogen sulfide to sulfur dioxide, then converting the resulting sulfur dioxide plus the remaining hydrogen sulfide to sulfur by low temperature Claus conversion, preferably below the solidification (freezing) point of sulfur (about 240.degree. F.).
It will be readily appreciated by those skilled in sulfur recovery that additional improved processes which can be selected for specific uses to meet the technical and environmental requirements of the specific application in an economic and efficient way are highly desirable.